1. Field of the Invention
The embodiments disclosed relate generally to gas turbine engines and, more particularly, to scalloped turbine inlet guide vanes with enhanced mass flow handling capabilities and methods to increase the mass flow rate in gas turbine engines.
2. Description of the Related Art
In a gas turbine the pressure of the air ingested into the engine is increased in a compressor before the burning of fuel in the engine's combustor significantly increases its energy level, generating gases at elevated temperatures. Then, these hot gases exiting the combustor are first turned from the axial flow direction into a desired orientation by a set of inlet guide vanes or nozzles before expanding through a series of rotors and stators of a turbine, thereby producing power to drive the compressor, which is connected to the turbine by a mechanical shaft. In an aircraft engine, the remaining available thermal power of the hot exhaust gases is converted into kinetic power in the engine's nozzle, thus producing thrust to power the aircraft. In a power generating gas turbine, further expansion of the hot gases through a power turbine generates electrical power by a generator connected to the power turbine by the same or another mechanical shaft. Those of ordinary skill in the applicable arts appreciate that, for a given compressor pressure ratio and turbine inlet temperature limit, the output power of these gas turbines increases as the mass flow rate of gases flowing there through increases. However, one of the limiting factors controlling the mass flow through the engine is the throat or minimum area of the inlet guide vanes, which, under normal operating conditions, operate under choked flow conditions.
FIG. 1 illustrates a conventional inlet guide vane or nozzle segment 10 that includes a plurality of blades or airfoils 12, each having a leading edge 14, a trailing edge 16, a suction or convex side 18, and a pressure or concave side 20. As know in the art, inlet guide vanes in gas turbine engines are normally composed of a plurality of vane segments 10 disposed next to each other around the engine shaft. These inlet guide vanes and nozzle segments 10 may include two or more blades per segment and the number of blades in a segment in no way limits the subject matter being disclosed herein. As shown in FIG. 1, the plurality of blades 12 is disposed between an inner platform 22 and an outer platform 24. The flow path for the hot combustion gases through the conventional guide vane or nozzle segment 10 is defined on one side by the convex side of a blade 12, on the other side by the concave side of an adjacent blades 12, on the top by an inner surface 26 of the outer platform 24, and on the bottom by an inner surface 28 of the inner platform 22. As shown in FIG. 1, a flow path profile 30 of the conventional guide vane or nozzle segment 10 is substantially a straight line, defining a throat area 32 towards the exit of the device. In a conventional engine, enlargement of the throat area 32 of the inlet guide vane or nozzle segment 10 has been accomplished by material removal from either the suction side or the pressure side of each blade 12 in the region near the trailing edge 16. However, as known in the art, the removal of blade material at the noted locations is undesirable because of both the alteration of the velocity triangle of the flow exiting the inlet guide vane or nozzle segment 10 and the generation of wake turbulence, both of which cause a deterioration of performance and a decrease in the overall efficiency of the engine.
It would therefore be desirable to develop an inlet guide vane or nozzle segments that will allow for expedited redesign so as to increase flow function and, therefore, optimize performance of new or existing gas turbines with negligible or no alteration of velocity triangles and wake turbulence, while reducing the overall development lead time and minimizing development and fabrication risks and associated costs.